well as the shoreline between FE and the dis- 

 charges, approach the physiological limits for sur- 

 vival of Fucus. It is likely that slight changes in 

 summer maximum ambient water temperatures, 

 and plant operating levels during critical periods, 

 will affect the Fucus population at FE. 



Chondrus 



Chondrus crispus is a bushy, perennial red alga 

 that is the dominant species in the low intertidal 

 zone at most stations. Chondrus contributes to 

 community stability by maintaining extensive 

 populations through time. In both pre-op and 

 3-unit operational periods, Chondrus occupied 

 from 4-80% of the Zone 3 substrata (average ca. 

 45%, Fig. 8 a,c), excluding FE which is discussed 

 separately. Station-to-station variability of 

 Chondrus abundance existed; MP and WP showed 

 consistently high (70-80%), and FS consistently 

 low (ca. 10%) Chondrus abundance in Zone 3 

 for both operational periods. 



Chondrus grows as a clump of upright stalks 

 from a basal crust; longevity of the stalks is 2-3 

 years, and the crust may live 6 years or longer 

 (Ring 1970; Taylor and Chen 1973). Young 

 stalks continually grow up to replace old ones 

 that are lost. Occasionally, processes occur that 

 remove stalks of all ages. A period of extremely 

 low tides concurrent with extremely cold temper- 

 atures in February 1980 exposed Chondrus to le- 

 thal conditions (NUSCO 1982, 1983), and was 

 responsible for the general decline in local 

 Chondrus abundance in the following spring. 

 Similar events, on a smaller scale, have occurred 

 in nearly every winter of our study. Regrowth 

 from surviving crustose holdfasts occurs relatively 

 quickly (Prince and Kingsbury 1973), maintaining 

 Chondrus as the dominant species in the low 

 intertidal zone at most rocky intertidal sampling 

 stations. 



If the basal crust of Chondrus is daTiaged or 

 removed, recovery of the population is much 

 slower, on the order of 3-5 years (Ring 1970; 

 Lubchenco 1980; NUSCO 1987). This extent of 

 damage was seen only at Fox Island-Exposed. 



When temperatures exceeded 28 °C at FE in Sep- 

 tember 1984, Chondrus was eliminated from the 

 community and was replaced by opportunistic, 

 ephemeral algae; the subsequent community was 

 described in detail in past aimual reports (NUSCO 

 1985, 1986, 1987). CAort</rwj has not re-established 

 itself at FE since September 1984, and has only 

 appeared in one low intertidal quadrat as a few 

 young fronds in summer 1987 (Fig. 8). Codium 

 fragile, a green alga, is now the dominant com- 

 ponent of the FE community, especially in the 

 low intertidal zone. Upright portions of Codium, 

 like Chondrus, are vulnerable to freezing and win- 

 ter fragmentation (Fralick and Mathieson 1972; 

 Ramus 1972), but, also like Chondrus, the surviv- 

 ing basal portion can regenerate new uprights in 

 spring. Unlike Chondrus, Codium can tolerate 

 the maximum summer temperatures measured at 

 FE. 



Chondrus serves as substratum for a large variety 

 of epiphytic plants and animals. In some cases, 

 this epiphytism has been found to cause shading 

 that is harmful to underlying Chondrus (Menge 

 1975; Lubchenco and Menge 1978), and for this 

 reason the abundance of two major epiphytes on 

 Chondrus, Monostroma and Polysiphonia, is pre- 

 sented for discussion. Monostroma shows peaks 

 of abundance in spring, March-May (Fig. 8). 

 Maximum cover at most stations is 5-10%; at 

 FS, peaks are only 1-2% (owing to lack of 

 Chondrus), and at SE, peaks are 20-40%. At FE, 

 maxima prior to the opening of the second cut 

 were 20-40%, and zero subsequently. Abundance 

 of Polysiphonia peaks in autumn, August-October, 

 with maxima comparable to that of Monostroma. 

 Again, the seasonal periodicity was disrupted at 

 FE. 



Fox Island-Exposed was the only station in ei- 

 ther the pre-op or 3-unit operational period where 

 Chondrus and epiphytes were affected by elevated 

 water temperature. Like Chondrus, Monostroma 

 has not returned to FE; its absence began in 

 spring 1984, probably as the result of increased 

 competition for space with Polysiphonia after the 

 second quarry cut was opened in August 1983. 

 Abundance of Polysiphonia peaked at 55% in 



Rocky Intertidal Studies 



37 



